Yahoo Japan has defended its online trade in ivory amid mounting pressure calling on the company to stop selling thousands of products on its auction site.

The company sold an estimated 12 tonnes of elephant tusks and fashioned pieces of ivory on its Japanese auction site between 2012 and 2014, prompting the activist network Avaaz to launch a petition that has attracted more than 1m signatures.

Referring to the trade as Yahoo’s “bloody secret”, the petition calls on the chief executive of the company, Marissa Mayer, and Japanese head, Manabu Miyasaka, to “urgently stop all ivory sales from sites/platforms in Japan and all other markets”.

“As global citizens, we are appalled that you allow ivory to be sold … fuelling elephant extinction,” the petition says.

On Wednesday, the company defended the practice, insisting that it prohibited the sale of raw ivory and ivory products that violates a 1989 trade ban.

The firm said its auction site permitted only the sale of items that were produced before the ban went into effect. “Since there is a chance some sales may be illegal we are strengthening our policies. If we find a sale was illegal we cancel it straight away,” Takako Kaminaga, a Yahoo Japan spokeswoman, said. “We ‘patrol’ 24 hours a day.”

Yahoo Japan is a joint-venture between Yahoo and the Japanese telecoms firm SoftBank. SoftBank said it had no comment.

Yahoo Japan came under fire from the UK’s Environmental Investigation Agency(EIA) in April 2015 for its sale of whale and dolphin meat. The company is Japan’s only online retailer that continues to sell whale and dolphin products.

Last year, the EIA also accused Japan of undermining international efforts to protect Africa’s elephants by failing to crack down on illegal registration practices. An EIA report claimed that a large majority of Japanese ivory traders were involved in illegal tusk registration activity, enabling them to “legalise” more than 1,000 tusks a year since 2011.

The report said that of 37 Japanese ivory traders approached by Japanese investigators posing as sellers of whole tusks, 30 offered to engage in illegal activities, including buying and processing unregistered tusks of unknown origin, and registering tusks using false information.

“Traders talked freely about how to evade or defraud the system and clearly had no reason to believe the government of Japan would ever look very carefully at their activities,” the report (pdf) said.

In September, the US and China agreed to work toward a near total ban on the ivory trade. Amazon and Google have both banned the sale of ivory on their sites.

Kaminaga suggested Yahoo Japan had not ruled out a change in its policy on ivory sales. The company was in contact with Japan’s environment ministry and other agencies, as well as with Yahoo and other shareholders, she said.

Asked if the firm was considering its position, she added: “You can’t say there’s absolutely no intention to change.”

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